GEN SET FIELD REGULATOR CIRCUIT

[videoeng1]

Hello everyone. I am looking for a regulation circuit for a AC generator. Unit is 35 years old and I want to replace ancient(and bad) field regulator/exiter. The required voltage for the field is about 50 to 70 volts DC @ 5A. to generate 3 phase 120/208V AC.(depending on load, of course)
The static resistance of the field winding is about 10 ohms.
Any schematics will be very helpfull, I can R&D something as long as it gets me in the ballpark.
Thanks, Chris

 

[CarlPugh]

I did something similiar about 20 years ago. Used a variable transformer, stepdown isolation transformer, bridge rectifier and filter capacitor. Worked great. Generator output regulation wasn't too bad without any feedback.
Don't fuse the field. If the fuse opens, there is a large inductive kick and something is likely to fail.
There should probably also be a rectifier across the field so that if power is suddenly removed, there is no inductive kick.
Good Luck
Carl Pugh

 

[nbucska]

send spec's <nbucska@pcperipherals.com>

 

[videoeng1]

Thanks Carl for the input and nbucska for the interest. I've actually already tried using a Variac transformer to feed the field, but there is feedback from gen. output to field. At a certain point the loop will become unstable, an increase in gen output will increase output of var. xfmr which increases field voltage( and current)and so on and on, it runs away up to 300v! Did your isolation xfmr have some regulating quality? Did you have any similar experiences? I know you can just buy an AVR from many places but there expensive!

 

[CarlPugh]

Should have given more details, The generator we used was driven by a 60 hertz electric motor. The power to the variable transformer was 115 volt, 60 hertz.(Generator was used for 400 hertz testing of transformers)
If you are using a gas engine, then you will probably have to use a regulated power supply or a seperate source for generator field power.
Anyway Good Luck
Carl Pugh